On demand cross web perforation

Abstract

A moving web is either perforated or cut using a knife cylinder having at least one blade, and an anvil cylinder having at least one raised anvil surface, and preferably a plurality (e.g. about 22) of alternating substantially uniform raised surfaces and depressions. The knife cylinder is substantially continuously rotated, and the anvil cylinder is substantially continuously rotated by a servo motor, which also positively controls the position of the anvil cylinder with respect to the knife cylinder to selectively either effect perforation or cutting of the web, or no perforation or cutting. Position controlling is typically accomplished by substantially constantly and instantly indexing the anvil cylinder in a reverse direction. Sensors may be utilized for sensing the locations of the knife and anvil cylinders and providing that information to a computer controller to facilitate indexing.

What is claimed is: 
     
       1. A method of acting on a moving web to effect perforation or cutting thereof, using a knife cylinder having at least one cutting or perforating knife blade and an anvil cylinder having at least one raised anvil surface for cooperating with the knife blade to effect cutting or perforation, and at least one depression adjacent the raised surface which does not effect perforation or cutting when cooperating with the knife blade, comprising the steps of: (a) substantially continuously rotating the knife cylinder in substantial registration with the moving web;   (b) substantially continuously rotating the anvil cylinder; and   (c) while practicing steps (a) and (b), positively controlling the position of the anvil cylinder with respect to the knife cylinder so that selectively said one raised anvil surface or said one depression is brought into operative association with the knife blade to selectively effect perforation or cutting of the web, or no perforation or cutting, respectively.   
     
     
       2. A method as recited in claim 1 wherein steps (b) and (c) are practiced by rotating the anvil cylinder with a servo motor, and phase shifting the anvil cylinder to change between perforating or cutting, or non-perforating or non-cutting, positions. 
     
     
       3. A method as recited in claim 2 wherein the anvil cylinder comprises a plurality of substantially uniform alternating raised surfaces and depressions; and wherein step (b) is practiced by rotating the anvil cylinder in a first direction; and wherein step (c) is practiced by substantially constantly and substantially instantly indexing the anvil cylinder in a direction opposite the first direction. 
     
     
       4. A method as recited in claim 3 wherein a computer controller is provided operatively connected to the knife and anvil cylinders, and comprising the further steps of sensing the locations of the knife and anvil cylinders and providing the sensed location information to the computer controller to facilitate practice of step (c). 
     
     
       5. A method as recited in claim 2 wherein step (c) is practiced by phase shifting the anvil cylinder between about five-ten degrees during each indexing action. 
     
     
       6. A method as recited in claim 1 wherein the anvil cylinder comprises a plurality of substantially uniform alternating raised surfaces and depressions; and wherein step (b) is practiced by rotating the anvil cylinder in a first direction; and wherein step (c) is practiced by substantially constantly and substantially instantly indexing the anvil cylinder in a direction opposite the first direction. 
     
     
       7. A method as recited in claim 1 wherein a computer controller is provided operatively connected to the knife and anvil cylinders, and comprising the further steps of sensing the locations of the knife and anvil cylinders and providing the sensed location information to the computer controller to facilitate practice of step (c). 
     
     
       8. A method as recited in claim 6 wherein step (c) is practiced by phase shifting the anvil cylinder between about five-ten degrees during each indexing action. 
     
     
       9. A method as recited in claim 1 wherein step (a)-(c) are practiced to effect perforation of the web. 
     
     
       10. A method as recited in claim I wherein steps (a)-(c) are practiced to effect cutting of the web. 
     
     
       11. Apparatus for cutting or perforating a web, comprising: a knife cylinder having at least one cutting or perforating knife blade extending outwardly therefrom;   an anvil cylinder having a plurality of substantially uniformly alternatively raised anvil surfaces for cooperating with said knife blade to effect cutting or perforation, and depressions adjacent the raised surfaces which do not effect perforation or cutting when cooperating with a said knife blade;   a drive mechanism for driving said knife cylinder; and   a servo motor operatively connected to said anvil cylinder to effect rotation thereof and for positively controlling the location of said anvil cylinder with respect to said knife cylinder during rotation of said anvil cylinder to selectively provide perforation or cutting, or no perforation or cutting.   
     
     
       12. Apparatus as recited in claim 11 wherein said anvil cylinder comprises between about 20-25 each of said alternating raised surfaces and depressions. 
     
     
       13. Apparatus as recited in claim 11 further comprising a computer controller for controlling operation of said servo motor; and a position sensor associated with each of said knife cylinder and said anvil cylinder for providing position information to said computer controller. 
     
     
       14. Apparatus as recited in claim 11 wherein said at least one blade comprises two blades spaced approximately 180 degrees from each other. 
     
     
       15. Apparatus for cutting or perforating a web, comprising: a knife cylinder having at least one cutting or perforating knife blade extending outwardly therefrom;   an anvil cylinder having a plurality of substantially uniform anvil surfaces for cooperating with a said knife blade to effect cutting or perforation, and a plurality of substantially uniform depressions alternating with said raised surfaces which do not effect perforation or cutting when cooperating with a said knife blade;   a first drive mechanism for driving said knife cylinder; and   a second drive mechanism for rotating said anvil cylinder in a first direction; and for substantially constantly and instantly indexing said anvil cylinder in a direction opposite the first direction to provide either perforating or cutting, or no perforating or cutting.   
     
     
       16. Apparatus as recited in claim 15 wherein said anvil cylinder comprises between about 20-25 each of said alternating raised surfaces and depressions. 
     
     
       17. Apparatus as recited in claim 15 further comprising an encoder operatively connected to said knife cylinder.